Abstract
Intramoleclar acylation of the sulfur-stabilized carbanions of the acyclic ester 9 and amide sulfides 11 was carried out as a model study for developing an effective method for the construction of medium-ring ketones by ring closure. Reaction of 9a-c or 11a-g with lithium diisopropylamide (LDA) proceeded smoothly and the expected keto sulfides 10a-c or 12a-g, respectively, were obtained. In the cases where R1 and/or R2 in 11 were normal alkyl groups, the reaction did not take place. However, these difficulties were readily overcome either by introducing a methyl group next to the carbonyl group or by converting the sulfides into the corresponding sulfoxides or sulfones. Acylation in the allyl sulfides 11b, d, f and the allyl sulfone 20b takes place at the α-position to the sulfur atom, yielding β, γ-unsaturated ketones. A reductive removal of the sulfide moiety or its conversion into other functional groups was also examined.
